The I-Team has learned that an internal investigation is under way to determine why the Chicago Marathon ran out of medals for more than 1,000 finishers.

This Intelligence Report looks at what may have happened to the missing medals.

For now this is the case of the missing marathon medals. Organizers of the 35th annual Chicago Marathon say they ordered enough medals for everyone who deserved one -- that would be all those who finished in less than 6 hours, 30 minutes. Race officials are at a loss to explain what happened to the medals for at least 1,300 runners.

Even though the maximum 45,000 runners signed up for the marathon and paid the $150 entry fee, not all of them actually run in the race or finish, nor do all cross the line within the maximum 6 1/2-hour time.

About 36,000 marathoners usually finish. Marathon officials say they have rechecked their records that show more than enough of these medals were ordered for all participants.

Of course, the first place finishers got theirs, from Governor Pat Quinn and Mayor Rahm Emanuel, and most of those who followed did too, but when runners began crossing the finish line at about 6 or 6 1/2-- well within the official race window -- there were no medals.

Just as race officials had mysteriously run out of race shirts for all the participants who signed up, suddenly, the medals were gone too.

After running 26.2 miles, and making it to the finish line, at least 1,300 paid marathoners walked away empty handed.

The I-Team asked marathon officials Monday if the medals might have been stolen or inadvertently hidden in someone's car trunk, like election ballots sometimes are.

A spokesperson told the I-Team they have launched an investigation to find out what happened.

"As part of our efforts to understand how this occurred, we confirmed that we did purchase more than enough medals," the I-Team is told. "Knowing this, we are looking into the reasons why we did not have enough medals at the finish line. This includes interviewing staff and volunteers at the finish line, checking inventory delivered into Grant Park, talking to security and more."

As some of those lucky enough to get medals were having theirs engraved Monday, race officials promised that everyone entitled to a medal will eventually receive one in the mail.

A shipment is expected Tuesday morning, and officials expect to get them out quickly. Officials say that anyone who did not receive a medal after the race should expect a medal by the end of the week.

The race director, Carey Pinkowski, says staffers are looking into what happened to the missing medals and are going over the entire process to ensure it does not happen again.

"I'm terribly sad that some of our finishers did not receive a medal," said Pinkowski on Monday. "Our primary responsibility today [is] to get to our vendors, suppliers, to get some medals into Chicago, and we'll receive those tomorrow, and get those out as quickly as possible."

The Chicago Marathon is one of the city's most prominent acts on the world stage and has grown to become respected as a well-run international sporting event.

Now, race organizers are in damage control mode, telling the I-Team they "feel terrible" about what happened and are working to do whatever is necessary to make things right.